The presence of severely abnormal behavior, such as self-injurious behavior (SIB) in laboratory housed primates compromises the quality of the animal research resource and adversely impacts research. In rhesus monkeys, SIB consists of intense, self-directed biting that can result in serious wounds requiring veterinary treatment. Based on findings from our laboratory and others, we have developed a model proposing that SIB arises from adverse life events, is maintained by dysregulation of several neurochemical and physiological systems, and functions to reduce anxiety. Unfortunately, SIB is resistant to treatment, alleviated neither by environmental enrichment nor changes in cage size. Pharmacological treatments have shown effectiveness in reducing SIB; however, relapse is common post-treatment, and long-term maintenance on drugs is undesirable for research purposes. The long-term goal of this project is to decrease the prevalence of SIB in captive primates by (1) preventing the onset of SIB through identification of key risk factors, and (2) developing novel treatments for this disorder that are cost-effective and produce long-lasting benefit. In furtherance of this goal, the proposed project will test the hypothesis that stress exposure and anxious behavior are precipitating factors in the development of SIB. To determine the generality of this hypothesis, factors contributing to SIB onset will be studied at 4 national primate research centers. To reduce the incidence of SIB in animals that have already developed this disorder, we will test a novel pharmacotherapeutic approach involving administration of the opioid receptor antagonist naltrexone. Short- term treatment with naltrexone has been shown to yield long-term decrements in SIB in many human patients, but this compound has not yet been tested on non-human primates. Finally, hair plucking (another type of SIB) and more generally hair loss have come under increased scrutiny from federal regulators. Consequently, we have enlarged the scope of this project to include hair loss, and we will test the hypothesis that hair loss in captive primates can result from several different factors, including hair plucking, stress and anxiety, and atopic dermatitis.